Stepper motor

[Massimo]

Hi all,
does anyone know the correct procedure to replace a stepper motor?
Engine is perfect when warm but it cuts out when cold so i tought it was the stepper and i replaced it with a new one. Ecu resetted as well. Problem is still there and it's even worse now. Any idea? is there just one screw to set idling? Do you know what the other plastic part not too far from the stepper is? it's connected to electric wires too and it's not on the same side of the stepper but in the front-top of the engine. Thank in advance for any help.

[CJ]

Massimo, check the wiring on the stepper plug - the wires have been known to break, this may not be obvious on first look.

CJ

[Massimo]

Thanks CJ, i'll check it again but i'm afraid it's ok

[sinlessgunner]

Same problem with mine but this is why I don't want to buy a new one!! In case it's the wiring or something. Gonna have a very close look and an examination with a voltmeter this evening I think!!

[Massimo]

I double checked wiring today and it's fine. I can't beleave the new stepper motor is faulty too...any suggestion?

[CJ]

Massimo, suggest you undertake a diagnostic to see if any of the sensors are playing up

http://www.ftowa.com/html/workshop/workshopart07.html

CJ

[steelroe]

Massimo, the new motor is prob not faulty. On some FTO's it is not just a simple matter of installing the new stepper, you have to adjust the Idle screw aswell. see here for more info http://www.camskill.co.uk/products.php?plid=m3b0s9p362
see under note 1

[steelroe]

Ther is also a test prodedure in the manual for the stepper motor.

[Massimo]

Do you know how to set the TPS back to the default position?
I messed a lil bit with it and i don't know how to get back

[steelroe]

There is a detailed procedure in the manual on how to adjust it. Not too hard if I remember right.

[CJ]

Did you remove from the throttle body? If so, then you should be OK. Ideally, you need to measure the high and low voltages / resistance with a multimter to ensure they're in tolerance, get searching through the workshop manual. Alternatively, if you have access to another FTO, you could check the orientation on the TB and mimic the position on your own.

If the TPS tolerances are out, the engine will idle erratically and cut out when the the revs drop down low.

CJ

[Massimo]

Massimo, the new motor is prob not faulty. On some FTO's it is not just a simple matter of installing the new stepper, you have to adjust the Idle screw aswell. see here for more info http://www.camskill.co.uk/products.php?plid=m3b0s9p362
see under note 1

I followed that procedure with no luck...the engine just don't idle when cold. i'll try the diagnostic suggested by CJ... i think the ECU doesn't tell to the stepper what to do cause there no difference at all if i unplug it. The stepper is not working at all anyway, so it could be a faulty sensor not telling the ECU the right information. I think it'll be hard to fix it myself.

[CJ]

i'll try the diagnostic suggested by CJ... so it could be a faulty sensor not telling the ECU the right information. I think it'll be hard to fix it myself.

The diag will tell yuou exactly what sensor is at fault (if at all), replacing sensors is usually straightforward. Run the diag and let us know the result.

CJ

[Massimo]

I ran the diag. today and it gave 12- air flow sensor?!It did 1 long flash and then 2 short ones.Do u know where's this sensor and how can it be fixed.
Cheers

[steelroe]

Air flow sensor is just behind the air filter box. It is the square thing behind thew filter in this link.
http://www.camskill.co.uk/products.php? ... b0s123p161

I have seen a few of these give trouble.
I would reset the ecu and test again to see if this fault is logged after a good drive. Possibly this fault is there with a while.

[steelroe]

Get your TPS back in the correct position first, as per manual,and then start again.

You now have a good starting point given the code you extracted.

[Massimo]

From the workshop manual :


IDLE POSITION SWITCH AND THROTTLE POSITION SENSOR
ADJUSTMENT (VEHICLE WITHOUT TCL)

1. Connect the MUT II to diagnosis connector

If the MUT II is not used, follow the steps below.
- Disconnect the throttle position sensor connector
- Connect the special tool (TPS test harness) to the throttle position sensor connector.
- Connect an ohmmeter between the terminal NO. 2 and the terminal NO.1 of the throttle position sensor connector.

2. Insert a thickness gauge with a thickness of 0.65 mm between the fixed SAS and the throttle lever.
3. If the MUT II is used turn the ignition switch to ON.
4. Loosen the throttle position sensor mounting bolt, and then turn the throttle position sensor clockwise as far as it will go.
5. Check that the idle position switch is ON at this position.
6. Slowly turn the throttle position sensor counterclockwise and find the point where the idle position switch turns off (no continuity between idle position switch terminal and sensor earth terminal).
Securely tighten the throttle position sensor mounting bolt at this point.
7. If the MUT II is not used, follow the steps below.
Connect the released throttle position sensor harness-side connector to the special tool.
Connect a digital voltmeter between the terminal NO. 3 and the terminal NO. 1 of the throttle position sensor connector.
Turn the ignition switch to ON.
8. Check the throttle position sensor output voltage.
Standard value: 400 – 1,000 mV
9. If there is a deviation from the standard value, check the throttle position sensor and the related harness.
10. Remove the thickness gauge.
11. Turn the ignition switch to OFF.
12. Disconnect the MUT II. When the MUT II is not used remove the special tool and connect the throttle position sensor connector.

Anything is clear to me except points 8 and 9...How do i adjust the position of the sensor without the MUT II? which value between 400 and 1,000 do i need to read on the voltmeter to get the right position? Any suggestion?